In an assembly line for automobiles or the like, a so-called jig pallet is used, which has jig functions in the pallet.
FIG. 15 is a schematic view showing a fuel tank mounting device for use in an assembly line for automobiles. As shown in FIG. 15, a part of complex shape and which is susceptible to deformation, such as a fuel tank 1, is fed from a subline and is placed on a jig pallet 2.
The prior art jig pallet 2, as shown in FIG. 16 (plan view) and FIG. 17 (front view), comprises a base plate 3 with a plurality of columns 4 mounted on it. A flange portion 1a of the fuel tank 1 contacts against the top ends of the columns 4 and is positioned by engaging pins 6 located at the top ends of the columns 4 which engage in location holes 5 formed in the flange portion 1a.
A cutout 3a is provided at the center of the base plate 3. The cutout 3a accommodates a chucking device comprising an air cylinder 8 and a bell crank 9 supported by a carrying arm 7 on which the jig pallet 2 is mounted. Numerals 10 and 11 indicate location holes and pins to position the base plate 3 with respect to the arm 7, and numeral 12 indicates a pressure roller attached to the front end of the bell crank 9.
The device is used to mount a fuel tank 1 to a vehicle body 13 of any one of a variety of car models, and can accommodate various types of fuel tanks, which are then positioned against the lower side of the vehicle body 13.
Normally, the fuel tank 1 is mounted to the vehicle body 13 using fastener members such as bolts and nuts, and the fuel tank mounting device has a device to attach and tighten the fastener members. However, the fuel tank mounting device has had the following problems.
Depending on the car model, the fastener members include hexagonal bolts and nuts, machine screws, and the like, which may be of different diameters. Therefore, multiple types of driving tools (such as nut runners and screw drivers) are required to tighten the fastener members. This requires a complex drive control device to select the appropriate driving tools and guide them around the fuel tank 1.
Additionally, since workers cannot be placed in the vicinity of the mounting device for safety reasons, the fastener members must be automatically fed to the fastening locations.
The driving tools must be moved to pick up the fastener members from a feeder, or, the fastener members must be transferred by compressed air through a plastic hose. However, the former takes a time to move the driving tools, which leads to a retardation in line speed, and the latter has a problem of frequent jamming of the fastener members in the plastic hose, which causes stoppage of operation of the line.
Another example of a prior art fuel tank mounting device is described in Japanese Utility Model Publication Laid-open No. 63-35620/1988.